A carbon fiber fabric produced by weaving a warp yarn and a weft yarn made of a carbon fiber filament bundle (“fiber bundle” or simply “yarn” hereafter), obtained by bundling a plurality of carbon fiber filaments using a sizing agent, can be composited with a resin to form a composite and thereby reduce weight and increase strength. Such fabrics have accordingly been used widely in the field of aircraft materials. In recent years, there has been demand for the fabrics to be made even lighter while maintaining their strength.
Attempts to attain strength while reducing the amount of yarn (weight per unit area) used in the fabric have been made in order to satisfy such demands for a reduction in weight.
However, merely reducing the weight per unit area results in gaps being formed in the fabric; and, when the fabric is formed into a composite, results in the strength being insufficient and properties being inconsistent.
One method for solving the problem involves spreading each of the individual warp and weft yarns that form the fabric. Specifically, for example, there is disclosed in a patent reference 1 a method in which a jet of air is sprayed to spread the weft yarns (the yarns disposed orthogonal to the direction in which the fabric is conveyed), whereupon a surface of a reinforced fiber fabric being conveyed is subjected to pressure by a roller body that moves reciprocatingly in the longitudinal direction in which the fabric is conveyed (i.e., parallel to the warp yarns), whereby the warp yarns (the yarns disposed parallel to the direction of fabric conveyance) are spread. There is also known a method in which a fabric is immersed in water and opened using, for example, sound waves.    [Patent reference 1] Japanese Laid-open Patent Publication No. 2003-268669